The present invention relates to a lifting device for substrates and has a holder.
Such lifting devices are used, for example, during the manufacture of disc-shaped substrates, such as CDs or DVDs, in order to guide the substrates on a spindle relative to their height. With such devices, generally a plurality of spindles are provided for receiving the substrates on a rotary table. Each of the spindles is provided with a so-called spacer that surrounds the spindle and upon which are placed the respective disc-shaped substrates. In an operating position of the spindle, the support of the lifting device is brought into engagement with the spacer by a lateral movement of the entire lifting device. In this position of engagement, the spacer can be raised and/or lowered by the lifting device, and in particular as a function of whether the substrates are to be stacked upon the spindle and the spacer or are to be removed therefrom.
In order to bring a new spindle into the operating position for the receipt or removal of substrates, the lifting device must first be moved away from the spindle or spacer that is in engagement with the support. A new spindle is subsequently moved into the operating position, and the lifting device is brought back into the engagement position. In this connection, not only is a device for the lateral movement of the lifting device necessary, but sensors that sense the lateral position of the lifting device are also necessary, thereby increasing the susceptibility of the lifting device to breaking down. Furthermore, due to the lateral movement of the lifting device, a larger installation space is required.
U.S. Pat. No. 2,919,010 discloses a lifting device where an arm that carries a support is moved by a drive into contact with a substrate that is to be received, for example by means of a piston. In so doing, the support directly engages the substrate, whereby in particular with sensitive substrates damage can occur to the substrate. In order to bring the substrates into the region of the lifting device, in addition to the drive for the pivoting movement a separate drive is provided for moving the substrates.
DE-A-196 06 763 discloses a transport mechanism having a grasping device for holding and transporting substrates, with the grasping device being rotatable about an axis of rotation. In order to come into engagement with substrates, the grasping device is first rotated over a substrate and is subsequently moved linearly. In so doing, the grasping device is actively not only rotatable but also is driven linearly.
DE-A-36 28 544 discloses a magnetic holding device having magnetizable elements that are displaceable relative to one another and that are in the position due to relative displacement to adapt to the surface of the work piece. To receive the work piece, the magnetizable elements are magnetized and are secured relative to one another in order, when a magnetic force is applied, to prevent a relative displacement of the elements relative to one another.
Proceeding from the above mentioned state of the art, it is an object of the present invention to provide an economical apparatus that enables a spindle change in a simple and reliable manner.
Pursuant to the present invention this object is realized in that the substrate support can be brought into engagement with the substrate or a substrate holder by rotating or pivoting the substrate support, whereby the rotation or pivoting of the support is effected by a movement of the substrate holder. In this way, a simple spindle exchange is made possible without a lateral movement of the lifting device. This eliminates the drive for the lateral movement of the lifting device, as well as the sensors for sensing the lateral position, thereby eliminating the cost for these devices. The device overall requires fewer parts, thereby increasing the reliability of the device. By means of the passive rotation or pivoting of the support, there results a particularly simple control of the device, since only the movement of the substrate holder has to be precisely controlled.
Pursuant to one preferred specific embodiment of the present invention, the support is rotatable about a central axis.
To ensure that the support is disposed in a predetermined position when it is not in engagement with a substrate holder, the support is biased in a rest position. In this way, a respectively uniform engagement is achieved between the support on the one hand and the substrate holder on the other hand.
The biasing is preferably achieved by at least one magnet. By using as least one magnet, a biasing is achieved in a simple and reliable manner, whereby the drawbacks of mechanical devices, such as fatigue and/or failure of the mechanical parts, are avoided. Pursuant to one preferred specific embodiment of the present invention, at least one magnet is provided on a supporting arm of the lifting device and/or a plurality of magnets, especially four magnets, are provided on the support.
In order to provide a good engagement between the support and the substrate holder, and to thereby effect the rotation or pivoting of the support, the support is provided with preferably essentially radially projecting legs.
Pursuant to the presently preferred specific embodiment of the present invention, the support has a star shape with four or five legs.
The lifting device is advantageously furthermore provided with sensor means for sensing the lifting height of the substrate holder.